Process of esterifying cellulosic materials with vapors of lower fatty acids



Patented Sept. 15, 1931 f,juuireuj STATES PATENT OFFICE EANS r. CLARKE AND CARL J, MALM, or nocnns'rnn; NEW YORK, ASSIGNORS TO EAST- Ill/IAIN'KODAKCOMPANYQQF noonns'rnn', NEW YORK, A CORPORATION 01* NEW YORK rnoonss or nsrnnir'ymc' cELLULosic No Drawing.

This invention relates to processes ofesterifymg cellulosic materials withthe vapors of the lower fatty acids. containing more than one and less than 'eightcarbon atoms. This application continues that subject matter which is common to itand'our prior applicationsSerial No, 122,028,filed July 12th, 1926 for cellulose esters of fatty acids and, pro cesses of making the same, Serial No. 160,765,

filed January, 12th, 1927for process of esterify-ing; hydrated cellulose with lower fatty acidsand Serial No. 186,170, filed April 23rd,

' 1927) for processofesterifying mercerized cellulose with lower fatty acids which are Letters Patent #1,668,944, 1,668,945 and 1,687,059 respectively. 1

' Y 1 One oh'ect of our invention isto provide an combined in the ester by the subsequent treatment of .the esters formed in the first stage, thus effecting an economy inexpensive ingredients, such as'the anhydrids of the fatty acids, and eliminating the manipulations incident to the treatments with the acids in liquid form. Still another object oft-he in' Ivention isto provide a process of esterfying cellulosic material by means of the vapors of the lower fatty acids at temperatures which 'produ ce 'rapid esterifi'cation and in the absence of oxygen or catalyzers which would rapidly degrade cellulose and the cellulosic esters at such elevatedtemperatures. A further object is to provide a process of esteri'fying cellulosic material by means ofjthe vaporsof the lower fatty acids without subjecting said material to any esterifying or washing liquids during such esterification. Other objects will hereinafter appear,

cause of its well MATERIALS WITH VAPORS OF LOWER FATTY ACIDS Application filed June 21, 1927. Serial No. 200,502.

We have found that the above objects may be attained by subjecting cellulosic material to vapors of one or more of the fatty acids contalning more than one but less than eight carbon atoms at temperatures above 100 C.

and below the temperature at which degra dation of the product takes place,s'ay about 200 C. We have likewise found that the vapors of the acids should be substantially free from oxygen gas which causes very rapid,

deterioration of the cellulosic material'and the cellulose esters at such high temperatures. It is alsohighly preferable that any catalyzer, such as sulfuric acid, for example, be omitted during rnown deteriorating action on cellulosic materials at such temperatures. We have likewise found that when at least 4% of acetyl groups are combined with the cellulose by our vapor treatment, the lower r esters, thus produced, can be further acetylated and made chloroform-soluble, or acetone-soluble, by the customary methods, but withthe amount of fatty acid anhydrid correspondingly diminished. Thus from the standpoint of the final product the preliminary vapor esterification effects a very great economy, because it is much cheaper than the anhydrid which it enables the manufacturer to dispense with; Moreover, it obtains this economy withoutdegrading the materiahas is evidenced by the flexibility of films made from the final product. p

In our process we use the vapors of one or more of the fatty acids having more than one and less than eight carbon atoms, such as acetic, propionic, butyric, Valerie, caproic, heptylic, etc; But the rate of esterification falls off rapidly with the higher members of this group of acids. While this can, to a con- 1 siderahle extent, be counteracted by working at as high a temperature as possible, nevertheless, we prefer to use the lower members of the group, such as acetic acid, propionic acid and butyric acid. Of these, acetic acid is commercially the most important at ent, because of its lowereost.

For the cellulosic material we may use either plain cellulose, or mercerized cellulose, or hydrated cellulose obtainedby reversion,

presthis vapor treatment, be-

7 being between 20 and 40%..in typical stances.

..The highest speed acet ylation is obtaine d. when the vapor treatment is T carried out on fibersof rayon made. by'the viscose process, ortthe cuprammonlum process or the denitrated nitro-cellulose process. These 'aref-exampies' of so-called hydratodcellulose. l/Ve do not like to use in our process any cellulosic materialwhich has been so degraded by-hydrolysisor oxidation as to yield esters} which form brittle films. Some care,

therefore, is exercised testing the rayon fibers which are suitable for producing good productsiby our:processes. .lVhen suitable rayon fibers are treated, in the same way that the plain cellulose is treated in the hereinabove given eXamp-le,'the esterificamon by the vapors takes place relatively very rapidly and-the percentage of acetyl in fthefibers can be quickly brought above 8% so as to'e ffect notable economies in subsequent complete Yacetylation. v

leaves the fibers or particles of the variouscellulosis materials in substantially their original physical form, without causing them to swell orstick together, the handling of the materials is the simplest possible. They are merely put into the apparatus and then taken out at the end of. the esterification, without any need of washing out an excess of acid,

and thereby diluting and lowering the value of the latter. Nor is any drying step necessary.

, The lower acetyl celluloses, or other lower esters of the fatty acids, obtained by means of the vapors, possess increased susceptibility to further esterification, the latter being effected in any suitable known way. Thus, for

example, the subsequent acetylation to chloroform solubility can be carried out in a bath of acetic acid and acetic anhydrid containing zinc chlorid or magnesium perchlorate trihydrate as the catalysts. In such a bath, of

course, the percentage of anhydrid is cut. down soas to be only 60% to 80% of that -5 usually used.

Our vapor-csterified products are also useful in preparing mixed esters. Thus a cellulose acetate, prepared as hereinabove described and containing 8% of acetyl groups, may be further esterificd in any of the baths acetyl content.

cinnamic. and to parts. by weight of anhydride which impels esterification, such as chloroacctic anhydrlde, together with a catalyst, such as .05 parts by weight of mag 5 nesium perchlorate trihydrate. In this bath there are treated from 3 to 5 parts by weight of the cellulosic material, the operation being conducted at 60 to C. until a homogeneous dope is obtained, usually in from 3 to i 24 hours. Or, again, a cellulose propionate containing 15% of propionyl (prepared by exposingmercerized cellulose to the action of propionic acid vapor at 160-165 C. for

twenty hours). may be further esterified by means of acetic anhydrid in the presence of a suitable catalyst, when it yields an ester directly soluble in acetone.

-Having thus described our invention, what we claim as. new and desire to secure by Letters Patentis:

'1. In the process of making a cellulose ester of a fatty acid, heating esterifiable cellulosic material in the vapor of a fatty acid having more than one and less than eight carbon atoms at a temperature above C. and

below the temperature at which the product is degraded until'the acetyl group in the ester thus produced reachesat least 4%, said vapor being'the sole acetylating agent.

2. Inthe process of makinga cellulose ester of a. fatty acid, heating esterifiable cellulosic material. inthe vapor of a fatty acid having more than one and less than eight carbon atoms at atemperature above 100 C. but less than200 C. in the absence of oxygen gas and degrading catalysts until the acetyl group in the ester thus produced reaches at least 4%, said vapor being the sole acetylating. agent. 3. In the process of making a cellulose ester of acetic acid, heating esterifiable cellulosic materialin the vapor of acetic acid at a temperature above 100 C. and below 200 C. in the absenceof oxygen gas and degrading catalysts, until the acetyl group in the ester th-usproduced reaches at. least 4%, said vapor being the sole acetylating agent. e e

4. In the process of makinga cellulose ester of afatty acid, heating esterifiable cellulosic material in the superheated vapor of a fatty acid having more than one and less than eight carbon atoms at a temperature above 117 C. but below 200 C. in tl1e-absenceof oxygen gas and degrading catalysts, until the. acetyl group inthe ester thus produced reaches at least 4%, said vapor being the sole acetylating agent.

5. In the proc'ess of making a cellulose ester of a fatty acid, heating mercerized cel-' lulosein the vapor of a fatty acid having more than one andiless' than eight carbon atoms at a temperature above 100 C. but below the temperature at which the product is degraded, in the absence of oxygen gas, until the acyl group in the ester thus produced reaches atleast 8%, said vapor being I the sole acylating agent.

' ter of a fatty acid,.heating esterifiabl-eI cellu losic material in the vapor of a fatty acid having more than one and less than eight carbon atoms at a temperature above 100 C. and below the temperature at which the I product is degraded until the acyl group in the ester thusproduced reaches at least 4%, said vapor being the sole acylating agent, and thereafter further esterifying'the ester thus produced with additional acyl groups.

ther esterifying theester thus produced with additional acyl groups.

11. In theprocess of making a cellulose ester of a fatty acid, heating mercerized, cellulose inthe vapor of a fatty acid having more than one and less than. eight carbon atoms at a temperature above 100C. but below the temperature at'which the product is degraded in the absence of oxygen gas or degrading catalysts until the acyl group in the ester thus produced reaches at least 8%, and thereafter further esterifying the ester thus producedwith additional acyl groups by the aid of an anhy'drid and a catalyst,

12. In the process of making cellulose ace tate, heating mercerized' cellulose in acetic acid vapor at a temperature above 100C. but below 200 C. in the absenceof oxygen and degrading catalysts at superatmospheric pressure until the acetyl group in the ester thus produced reaches at least 8%, and thereafter further esterifying the ester thus produced with a mixture containing acetic anhydrid and a catalyst.

' Signed at Rochester,

New York,this 16th day of June, 1927;

HANS T. CLARKE. GAB-L J. MALM;

'8. In the process of making a cellulose es- I ter of a fatty. acid,heating esterifiable cellulosic-material in the vapor of a fatty acid having more than one and less than eight carbon atoms at a temperature above "100 C; but less than 200 C. in the absence of oxygen gas and degrading catalysts until the acyl group in the ester thus produced reaches at least 4%, said Vapor being the sole acylating agent, and'thereafter further esterifying the ester thus produced with additional acyl groups by the vaidlof an anhydrid and a catalyst. l 9, In the process of makinga cellulose esterof aceticacid, heating esterifiab-le cellulosic material in the vapor of acetic acid at a temperature above 100 C. and below 200 C. in the absence of oxygen gas and degrading catalysts, until the acetyl groupin the ester thus'produced reaches at least 4=%, said vapor being the sole acetylating "agent, and thereafter further esterifying the ester thus producedwith additional acyl groups by the aid of an anhydrid and a catalyst.

10."In the process of making a cellulose ester of a fatty acid, heating este-rifiable cellulosic material in the superheated vapor of a fatty acid'having morethan one and less than eight'carbon atomsat a temperature above 117 C. but below 200 C. in'the absence ofoxygen gas and degrading catalysts, until the acyl group the ester thus produced reaches at least 4%, said vapor being the sole acylating agent, and thereafter fur- CERTIFICATE OF CORRECTION.

Patent No. 1,823,350. Granted September 15, 1931, to

HANS T. CLARKE ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, line 38, for "cellulosis" read cellulosic; same page, line 103, claim 1, line 112, claim 2, and line 130, claim 4, for "acetyl" read acyl; same page, line 105, claim 1, line 114, claim 2, and page 4, line 2, claim 4, for "acetylating" read acylating; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of November, A. D. 1931.

M. J. Moore, (Seal) Acting Gommissioner of Patents. 

